I have the Lyman 57GPR on my Lyman and so far it is very accurate. The first day out with it I shot a 3 shot group at 75 yards that measured .28 inches center to center using 460NE's and 70gr of 777 3F. I haven't had a chance to shoot it in the last 2 months due to being out of town.

The 57 is a nice sight but not much use at the ranges your mentioning above. It works well for shots out to 200 or so yards depending on the load you use. New they cost well under $100 so they are much more afordable than what you were quoting.